This invention relates generally to water electrolysis systems. In particular, this invention relates to a fluid management system for a water electrolysis system which permits the conservation of water during steady state operation and the generation of high purity hydrogen and oxygen gases.
Electrolysis systems are energy conversion systems for producing hydrogen and oxygen gases from water. Typical electrolysis systems include a number of individual cells arranged in a stack with fluid, typically water, forced through the cells at high pressures.
Hydrogen or oxygen gases produced through electrolytic methods often contain: appreciable quantities of atmospheric gases, such as nitrogen, carbon dioxide, and argon due to atmospheric air diffusing into the process water; trace quantities of oxygen and hydrogen, respectively, due to diffusion across the electrolyte membrane; and contaminants, such as iron, sulfur, nickel, chromium, and chlorides, due to leaching from the system components into the water recirculation stream. In systems where these contaminants are not removed, they typically contaminate the electrolyte membrane or catalysts, thereby decreasing the electrolysis cell operation efficiency, and contaminating the product gas stream. Gases produced from the electrolysis cell in this manner must be subsequently purified using expensive filters.
A fluid management system for a typical proton exchange membrane electrolysis system is shown schematically in FIG. 1. A water and hydrogen mixture 60 exits the hydrogen side of electrolysis cell stack 61 and enters high pressure hydrogen/water separator 62. Product hydrogen 63 exits the separator and is directed to further processing (not shown). Hydrogen saturated water 64 passes from high pressure separator 62 to low pressure hydrogen water separator 65 which typically vents low pressure hydrogen gas 66 and collects water 67 in reservoir 68A drains into reservoir 68. Meanwhile, an oxygen/water mixture 69 exits the oxygen side of cell stack 61 and enters a cyclonic style phase separator 70 which vents oxygen gas 71 while collecting water 67 in reservoir 68. Water in reservoir 68 is pumped by pump 72 through deionizer beds 73, 74 and filter vessel 75. After deionizing and filtering, the water reenters the cell stack 61.
What is needed is a fluid management system which provides for contaminant free recirculated water utilizing a minimum amount of equipment, and eliminates the expensive filtering steps of existing fluid management systems.
The above-described drawbacks and disadvantages of the prior art are alleviated by fluid management system, the separation tank and the method of the present invention.
The phase separation tank comprises: an inlet for introducing water containing dissolved oxygen to the tank, a catalyst bed capable of reacting hydrogen and oxygen to form water and of removing cations and anions from the water; a water permeable filter for containing said catalyst bed, and a second inlet for introducing hydrogen to the catalyst bed.
The present invention method for recovering water in an electrochemical system, comprises: introducing an oxygen and water stream to a catalyzed bed within a tank, introducing a hydrogen dissolved in water stream to an interior area of the catalyzed bed, reacting the hydrogen and oxygen to form water, removing any ionic impurities from the water in the tank; and directing the recycle water to an electrochemical cell.
The above discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings.